Preparation of calcium alginate nanoparticles using water-in-oil (W/O) nanoemulsions

A procedure for the preparation of calcium alginate nanoparticles in the aqueous phase of water-in-oil (W/O) nanoemulsions was developed. The emulsions were produced from mixtures of the nonionic surfactant tetraethylene glycol monododecyl ether (C(12)E(4)), decane, and aqueous solutions of up to 2 wt % sodium alginate by means of the phase inversion temperature (PIT) emulsification method. This method allows the preparation of finely dispersed emulsions without a large input of mechanical energy. With alginate concentrations of 1-2 wt % in the aqueous phase, emulsions showed good stability against Ostwald ripening and narrow, monomodal distributions of droplets with radii <100 nm. Gelation of the alginate was induced by the addition of aqueous CaCl(2) to the emulsions under stirring, and particles formed were collected using a simple procedure based on extraction of the surfactant on addition of excess oil. The final particles were characterized using cryo-transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS). They were found to be essentially spherical with a homogeneous interior, and their size was similar to that of the initial emulsion droplets. The herein presented "low-energy" method for preparation of biocompatible nanoparticles has the potential to be used in various applications, e.g., for the encapsulation of sensitive biomacromolecules.     

Determination of metals in used lubricating oils by AAS using emulsified samples

An efficient method was developed for the determination of metals in used lubricating oils, by atomic absorption spectrometry. Oil samples were treated with an acid mixture and then emulsified in water (10% w/w) using ethoxy nonylphenol (6% w/w) as surfactant. Emulsion characteristics (oil, surfactant content and acid mixture) were optimized to obtain the best AAS signal. Good agreement was found between calibration curves of aqueous and emulsified standard solutions when a peristaltic pump was used to introduce the solutions into the flame. The emulsion methodology was comparable, within 95% of confidence, to traditional ashing methodologies when a standard reference oil and a used lubricating oil were analyzed. Precision between 0.4 and 5% RSD was obtained when real sample was analyzed using emulsions.     

Preparation of finely dispersed O/W emulsion from fatty acid solubilized in subcritical water

A novel method for preparing a finely dispersed oil-in-water emulsion is proposed. Octanoic acid dissolved in water at a high temperature of 220 or 230 degrees C at 15 MPa was combined with an aqueous solution of a surfactant and then the mixture was cooled. When a nonionic surfactant, decaglycerol monolaurate (ML-750) or polyoxyethylene sorbitan monolaurate (Tween 20), was used, fine emulsions with a median oil droplet diameter of 100 nm or less were successfully prepared at ML-750 and Tween 20 concentrations of 0.083% (w/v) and 0.042%, respectively, or higher. The diameters were much smaller than those of oil droplets prepared by the conventional homogenization method using a rotor/stator homogenizer. However, an anionic surfactant, sodium dodecyl sulfate, was not adequate for the preparation of such fine emulsions by the proposed method. Although the interfacial tensions between octanoic acid and the surfactant solutions were measured at different temperatures, they were not an indication for selecting a surfactant for the successful preparation of the fine emulsion by the proposed method.     

SYNTHESIS OF AMPHIPHILIC COPOLYMERS BASED ON ACRYLATES BY FREE-RADICAL POLYMERIZATION AND THEIR APPLICATION IN ALKYD EMULSIONS

Novel amphiphilic copolymers which contained poly(ethylene glycol) side-chain, long-chain alkyl pendant groups, and carboxyl groups have been synthesized by the conventional free-radical copolymerization of special monomers. The products were characterized by analysis of Fourier transform infrared spectroscopy (FT-IR), Gel Permeation Chromatography (GPC), and ¹H NMR. Based on the measurement of surface tension of aqueous copolymer solutions with various concentrations at an air/water interface, the critical micelle concentrations (CMC) was found to be lower along with the increase of copolymer concentration. Experimental results showed that CMC of this kind of amphiphilic polymer appeared in the range of 0.01～0.1 g/L. The amphiphilic polymer was mixed with an anionic surfactant (SDBS) in different proportions at aqueous solution and then successfully used in the preparation of alkyd emulsions. The results were compared with those of alkyd emulsions without polymeric surfactant. Steric stabilization of amphiphilic polymer was investigated by the observation of the stability of alkyd emulsions. The emulsions were stable after resting at ambient temperature for four months.     

Aqueous Emulsions of Polysyloxane Polyblock Copolymers as a Basis for Weatherproof Protective Coatings

On the way to solving the problem of developing an ecofriendly technology for preparing hydrophobic protective coatings to replace the existing technology involving casting from polymer solutions in toxic organic solvents, amphiphilic organosilicon oligomers, promising emulsifiers for preparing aqueous emulsions of organosilicon polymers, were synthesized. The synthesized oligomers were used to obtain stable aqueous emulsions of a film-forming silicone block copolymer. The resulting emulsions can be used to form hydrophobic protective coatings on the surface of construction materials. It was shown that the contact angle of wetting depends on the specific features of the preparation of the emulsion and reaches a maximum of 134°.     

Polyols,High Pressure,and Refractive Indices Equalization for Improved Stability of W/O Emulsions for Food Applications

Mixtures of polyols (glycerol, propylene glycol, glucose) and water were emulsified in oil (isopropyl myristate (IPM), medium chain triglycerides (MCT), long chain triglycerides (LCT), and d-limonene) under elevated pressures and homogenization, in the presence of polyglycerol polyricinoleate (PGPR), glycerol monooleate (GMO), and their mixture as emulsifiers to form water-in-oil emulsions. High pressures was applied to: a) the emulsion, b) the aqueous phase and c) the oil phase in the presence of the emulsifiers (PGPR and GMO). Under optimal pressure (2000 atms) applied to the ready-made emulsion or to the aqueous phase prior to its emulsification, and with optimal composition (30wt% polyol in the aqueous phase and MCT as the oil phase), the aqueous droplets were stable for months and submicron in size (0.1 μm). Moreover, due to equalization of the oil and the aqueous phases refractive indices, the emulsions were almost transparent. Pressure and polyols have synergistic effects on the emulsions stability. During preparation, surface tensions and interfacial tensions were dramatically reduced until an optimal water/polyols ratio was achieved, which allows rupturing of the droplets to submicronal size (0.1 μm) without recoalescence and fast diffusion to the interface. These unique W/O emulsions are suitable for preparing W/O/W double emulsions for sustained release of active materials for food applications.     

Thickening properties and emulsification mechanisms of new derivatives of polysaccharides in aqueous solution

The thickening properties of aqueous solutions of HHM-HEC (hydrophobically-hydrophilically modified hydroxyethylcellulose) and the emulsification mechanisms of HHM-HEC/water/oil systems were investigated. A dramatic increase in viscosity was observed with increased HHM-HEC concentration in water, caused by aggregation of hydrophobic alkyl chains. At higher concentrations of HHM-HEC (above 0.6 wt%) in water, it forms an elastic gel, which has good thixotropic properties and a high yield value. O/W (oil-in-water) type emulsions were obtained using HHM-HEC, which can emulsify various kinds of oil, including hydrocarbon, silicone, and perfluoropolymethylisopropyl ether. The viscosity of these emulsions depends only upon the oil volume fraction, not on the kind of oil. In addition, the oil particle size in the emulsions remained constant after a certain period because HHM-HEC formed a strong gel network structure and a protective layer, which prevented the emulsion from coalescing. Measurements of interfacial tension revealed that the alkyl chains in HHM-HEC did not significantly lower the interfacial tension at the water/oil interface when 0.5 wt% of HHM-HEC was added to water. Steady flow and oscillatory experimental results show that the rheological behavior of HHM-HEC/water/oil emulsions was similar to that of aqueous solutions of HHM-HEC. In the HHM-HEC/water/oil emulsion system, oil droplets were dispersed and kept stable in the strong gel structure of HHM-HEC. The aqueous solution of HHM-HEC showed salt resistance. It is thought to be due to sulfonic acid groups in HHM-HEC. The stability of the emulsion using HHM-HEC is based on both protective colloidal effects and associative thickening caused by alkyl chains in HHM-HEC.     

Sample preparation in the determination of metals in oil and petroleum products by ICP MS

Comparative elemental analysis of the Tengiz oil and diesel fuel is performed by inductively coupled plasma mass-spectrometry with autoclave digestion, digestion, dilution with organic solvents, and also rotating coiled columns (RCCs). The advantages and drawbacks of each of the listed sample preparation techniques for the separation of microelements are discussed. In contrast to the other versions, the use of RCCs is shown to provide a unique opportunity to preconcentrating microelements from oil and petroleum products into tiny volumes of aqueous solutions (10 mL of 0.5 M HNO₃). The eluate prepared can be used in the subsequent analysis by ICP MS with no extra sample preparation steps. The RCC preconcentration of elements from oil and petroleum products makes it possible to determine metals in concentrations from μg/kg to ng/kg.     

Long-term stabilization of foams and emulsions with in-situ formed microparticles from hydrophobic cellulose

We report a simple method to produce foams and emulsions of extraordinary stability by using hydrophobic cellulose microparticles, which are formed in situ by a liquid-liquid dispersion technique. The hydrophobic cellulose derivative, hypromellose phthalate (HP), was initially dissolved in water-miscible solvents such as acetone and ethanol/water mixtures. As these HP stock solutions were sheared in aqueous media, micron sized cellulose particles formed by the solvent attrition. We also designed and investigated an effective and simple process for making HP particles without any organic solvents, where both the solvent and antisolvent were aqueous buffer solutions at different pH. Consequently, the HP particles adsorbed onto the water/air or water/oil interfaces created during shear blending, resulting in highly stable foams or foam/emulsions. The formation of HP particles and their ability for short-term and long-term stabilization of interfaces strongly depended on the HP concentration in stock solutions, as well as the solvent chemistry of both stock solutions and continuous phase media. Some foams and emulsion samples formed in the presence of ca. 1 wt% HP were stable for months. This new class of nontoxic inexpensive cellulose-based particle stabilizers has the potential to substitute conventional synthetic surfactants, especially in edible, pharmaceutical and biodegradable products.     

Influence of Inorganic Electrolytes on the Stability and Structural and Rheological Properties of Emulsions Based on Rapeseed Oil

Formation conditions and structural and rheological properties were studied for emulsions based on rapeseed oil in the presence of aqueous solutions of sodium, potassium, and calcium chlorides and of sodium carbonate and sodium hydroxide.     

Surfactant polycomplexes in displacement processes of non-polar liquids from porous systems and demulsification of reverse emulsions

The surface properties of the polycomplexes of the non-ionic surfactant OP-10 with synthetic polyelectrolytes (polyacrylic acid, polymethacrylic acid, and polyethylenimine) at the water | (toluene + cyclohexane + hexane) interface were studied. It was found that at the low relative concentrations of OP-10 in the mixture (n = 0.05–1) the decrease in the surface tension is maximal. The displacement rate of the oil from the capillaries of different nature with aqueous solutions of various polyelectrolytes and OP-10 depends weakly on the nature of the capillary. The coefficient of oil displacement from porous systems with aqueous solutions of polycomplexes is higher by 18–25% than that of oil recovery with water. The study of the demulsifying properties of the polycomplexes showed that the lifetime of the reverse emulsions, including oil emulsions, is sharply decreased for large n values (n = 5–20).     

Emulsification of caraway essential oil in water by lecithin and β-lactoglobulin: emulsion stability and properties of the formed oil–aqueous interface

The stability and droplet size of protein and lipid stabilised emulsions of caraway essential oil as well as the amount of protein on the emulsion droplets have been investigated. The amount of added protein (β-lactoglobulin) and lipid (phosphatidylcholine from soybean (sb-PC)) were varied and the results compared with those obtained with emulsions of a purified olive oil. In general, emulsions with triglyceride oil proved to be more stable compared with those made with caraway essential oil as the dispersed phase. However, the stability of the emulsions can be improved considerably by adding sb-PC. An increase in the protein concentration also promoted emulsion stability. We will also present how ellipsometry can be used to study the adsorption of the lipid from the oil and the protein from the aqueous phase at the oil–water interface. Independently of the used concentration, close to monolayer coverage of sb-PC was observed at the caraway oil–aqueous interface. On the other hand, at the olive oil–aqueous interface, the presence of only a small amount of sb-PC lead to an exponential increase of the layer thickness with time beyond monolayer coverage. The amounts of β-lactoglobulin adsorbed at the caraway oil–aqueous interface and at the olive oil–aqueous interface were similar, corresponding roughly to a protein monolayer coverage.     

Pickering Emulsions Stabilized with Curcumin-Based Solid Dispersion Particles as Mayonnaise-like Food Sauce Alternatives

Pickering emulsions, which are emulsions stabilized by colloidal particles, are being increasingly positioned as novel strategies to develop innovative food product solutions. In this context, the present work aims to develop Pickering emulsions stabilized by natural-based curcumin-loaded particles produced by the solid dispersion technique as promising mayonnaise-like food sauce alternatives. Two particle formulations (KC1 and KC2) were produced using k-carrageenan as the matrix material and different curcumin contents, then employed in the preparation of three Pickering emulsion formulations comprising different oil fractions (φ) and particle concentrations (KC1 φ 0.4 (4.7%), KC2 φ 0.4 (4.7%) and KC2 φ 0.6 (4.0%)). The creaming index tests accompanied by the optical microscopy analysis evidenced the good stability of the developed products for the tested period of 28 days. The final products were tested concerning color attributes, pH, oxidative stability, textural, and nutritional composition, and compared with two commercial mayonnaises (traditional and light products). Overall, the produced emulsions were characterized by a bright yellow color (an appealing attribute for consumers), an acidic pH (similar to mayonnaise), and a considerably improved oxidative stability, implying a foreseeable longer shelf life. The sauce KC1 φ 0.4 (4.7%) showed a similar texture to the light commercial mayonnaise, being a promising alternative to conventional sauces, holding a low-fat content and potentially added benefits due to the curcumin and virgin olive oil intrinsic properties.     

Interfacial properties of emulsions stabilized with surfactant and nonsurfactant coated boehmite nanoparticles

The properties of emulsions stabilized with surface-modified boehmite particles of 26 and 8 nm in diameter have been investigated. The surface-modified particles were prepared by mixing aqueous dispersions of cationic boehmite particles with aqueous solutions of the surfactant p-dodecylbenzenesulfonic acid (DBSA) or the nonsurfactant p-toluenesulfonic acid (TSA). For the 26 nm particles, interfacial tension measurements indicate that p-dodecylbenzenesulfonic acid partitions between the particle surface and the oil-water interface, while p-toluenesulfonic acid remains on the particle surface. The partitioning of p-dodecylbenzenesulfonic acid supports the formation of emulsions, although in the absence of the particles the same surfactant concentration is not sufficient for emulsion stabilization. Due to the fast exchange kinetics, p-dodecylbenzenesulfonic acid is gradually replaced by particles. At equilibrium, the interfacial tension in the presence of the surface-modified particles is between the values for the pure particles and the pure surfactant solutions. However, the interfacial tension is independent of the surfactant concentration used in the preparation of the particles. Reducing the particle size to 8 nm leads to increased emulsion stability, and thus, the minimum particle concentration required to prepare stable emulsions was reduced to 0.1 g/L. However, above approximately 3.5 mmol/L of the sulfonic acids, the small particles dissolve slowly, and the emulsion stability is lost. This mechanism can be used to trigger the collapse of the emulsions.     

Effect of surfactants on the porous structure of poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) hydrogels prepared by an emulsion templating method

Stimuli-sensitive porous hydrogels prepared with an emulsion templating method developed by the authors are potentially applicable in the medical and pharmaceutical fields; thermosensitive N-isopropylacrylamide (NIPA) hydrogels having randomly distributed sphere-like cavities have been prepared by the polymerization in an aqueous phase in an oil-in-water (O/W) emulsion, followed by the washing of oil (oleyl alcohol) microdroplets. The surfactant plays a dominant role in the preparation of porous hydrogels and the pore size. This study concerns with the surfactant effects on the stability of pre-gel O/W emulsions. The porous NIPA hydrogels were successfully prepared using the surfactants forming the stable emulsion and their internal structures and swelling properties were characterized. The O/W emulsions and the porous hydrogels prepared using various amounts of oil and surfactant were characterized. The information obtained serves for preparation of porous hydrogels having suitable porous structure for their applications.     

Improved formulation of W/O/W multiple emulsion for insulin encapsulation. Influence of the chemical structure of insulin

W/O/W multiple emulsions are systems of potential interest in the oral administration of insulin. Although it has been shown that a single oral administration of insulin-loaded W/O/W multiple emulsion to diabetic rats led to the significant decrease of blood glucose levels (Silva Cunha et al., 1998, Int J Pharm 169:33), repeated administrations displayed unpleasant side effects such as diarrhoea and steatosis. These unwanted effects were attributed to the high oil concentration used for their preparation. In the present study, attention was focused on the reduction of oil concentration in the formulation of these systems and on the encapsulation of two different insulins. The physical properties and stability of the multiple emulsions over long periods of time were assessed by conductivity measurements, and granulometric and microscopic analyses. The encapsulation in the inner aqueous phase of two insulins, Umulin and Humalog, differing only by the transposition of one amino acid, had non-negligible effects on the formation and stability of W/O/W multiple emulsions. Both insulins were shown to improve the formation of the multiple emulsions. Circular dichroism studies and surface tension measurements evidenced the contribution of insulin conformation and surface properties in multiple emulsion formation and stability.     

Determination of sulphur in uranium matrix by total reflection X-ray fluorescence spectrometry

The possibility of sulphur determination in uranium matrix by total reflection x-ray fluorescence spectrometry (TXRF) has been studied. Calibration solutions and samples of sulphur in uranium matrix were prepared by mixing uranium in form of a standard uranyl nitrate solution and sulphur in the form of Na₂SO₄ standard solution, prepared by dissolving Na₂SO₄ in Milli-Q water. For major element analysis of sulphur, it was determined without separation of uranium whereas for the trace level determinations, uranium was first separated by solvent extraction using 30% tri-n-butyl phosphate (TBP) in dodecane as an extractant. In order to countercheck the TXRF results, a few samples of Rb₂U(SO₄)₃, a chemical assay standard for uranium, were diluted to different dilutions and sulphur content in these solutions were determined. The TXRF determined results for trace determinations of sulphur in these diluted solutions were counterchecked after addition of another uranium solution, so that sulphur is at trace level compared to uranium, separating uranium from these solution mixtures using TBP extraction and determining sulphur in aqueous phase by TXRF. For such TXRF determinations, Co was used as internal standard and W Lα was used as excitation source. The precision and accuracy of the method was assessed for trace and major element determinations and was found to be better than 8% (1σ RSD) and 15% at a concentration level of 1 μg/mL of sulphur measured in solutions whereas for Rb₂U(SO₄)₃, these values were found to be better than 4 and 13%, respectively.     

Determination of petroleum trace impurities in aqueous samples by chromatography in a steam flow

A procedure was developed for the determination of trace petroleum products in water by gas chromatography with steam as the carrier gas. Solid-phase microextraction was used for sample preparation. A method for the stabilization and homogenization of water samples before the analysis and a method for the removal of polar components of the sample were proposed. The precision and accuracy indices of the proposed procedure were estimated for aqueous solutions of a mixture of diesel fuel and oil with a concentration close to the maximum permissible concentration. The relative error in the measurement is no more than ～25% in the concentration range of petroleum products of 0.05–0.5 mg/L.     

Effect of the type of the oil phase on stability of highly concentrated water-in-oil emulsions

The water-in-oil high internal phase emulsions were the subject of the study. The emulsions consisted of a super-cooled aqueous solution of inorganic salt as a dispersed phase and industrial grade oil as a continuous phase. The influence of the industrial grade oil type on a water-in-oil high internal phase emulsion stability was investigated. The stability of emulsions was considered in terms of the crystallization of the dispersed phase droplets (that are super-cooled aqueous salt solution) during ageing. The oils were divided into groups: one that highlighted the effect of oil/aqueous phase interfacial tension and another that investigated the effect of oil viscosity on the emulsion rheological properties and shelf-life. For a given set of experimental conditions the influence of oil viscosity for the emulsion stability as well as the oil/aqueous interfacial tension plays an important role. Within the frames of our experiment it was found that there are oil types characterized by optimal parameters: oil/aqueous phase interfacial tension being in the region of 19–24 mN/m and viscosity close to 3 mPa s; such oils produced the most stable high internal phase emulsions. It was assumed that the oil with optimal parameters kept the critical micelle concentration and surfactant diffusion rate at optimal levels allowing the formation of a strong emulsifier layer at the interface and at the same time creating enough emulsifier micelles in the inter-droplet layer to prevent the droplet crystallization.